Over the past few years, lithium-ion batteries have begun replacing nickel-cadmium (NiCd), nickel-metal-hydride (NiMH), and lead-acid batteries in portable electronic devices such as personal computers as well as in portable power tools. As compared to these more conventional battery types, lithium-ion batteries typically employ more sophisticated charging schemes having stepped output current. For example, a battery charger may apply a pre-charge current having a lower amperage value to a battery pack before delivering a larger amperage current to the battery pack. Therefore, it is desirable for battery chargers to employ power supply circuits that can effectively deliver output current at different amperage values to a battery pack.
This section provides background information related to the present disclosure which is not necessarily prior art.